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Abstract:

There is provided a cleaning blade for an electrophotographic apparatus
having good cleaning performance both immediately after long-time
shutdown under low temperature environment and during continuous use
under low temperature environment even when spherical toner having a
small diameter is used. A cleaning blade for an electrophotographic
apparatus having an elastic blade member which is brought into contact
with an image bearing member and frictionally slid to remove remaining
toner, wherein the elastic blade member satisfies (1) to (4): (1) the
stress-relaxation rate represented by the formula (a) at 10° C. is
25% or less;
Stress - relaxation rate = Variation of
stress when left to stand at
10 % stretching state for 1
hour Stress at the moment of
10 % stretching × 100 ( a ) ##EQU00001##
(2) the international rubber hardness (IRHD) is 65 or more and 80 or less;
(3) the stress upon 100% stretching in a tensile test is 3.0 MPa or more
and 5.0 MPa or less; and (4) the peak tan δ temperature in a
dynamic viscoelastic test is -20° C. or more and 0° C. or
less.

Claims:

1. A cleaning blade for an electrophotographic apparatus having an elastic
blade member which is brought into contact with an image bearing member
and frictionally slid to remove remaining toner,wherein the elastic blade
member satisfies (1) to (4):(1) the stress-relaxation rate represented by
the formula (a) at 10.degree. C. is 25% or less; Stress -
relaxation rate = Variation of stress
when left to stand at 10 %
stretching state for 1 hour Stress
at the moment of 10 % stretching
× 100 ( a ) ##EQU00005## (2) the international rubber
hardness (IRHD) is 65 or more and 80 or less;(3) the stress upon 100%
stretching in a tensile test is 3.0 MPa or more and 5.0 MPa or less;
and(4) the peak tan δ temperature in a dynamic viscoelastic test is
-20.degree. C. or more and 0.degree. C. or less.

2. The cleaning blade for an electrophotographic apparatus according to
claim 1 wherein the elastic blade member is formed using a urethane
elastomer material.

3. The cleaning blade for an electrophotographic apparatus according to
claim 2 wherein the elastic blade member satisfies (5) to (7):(5) the
polyisocyanate concentration is 0.95 mmol/g or more and 1.15 mmol/g or
less;(6) the chain extender concentration is 0.25 mmol/g or more and 0.50
mmol/g or less; and(7) the urethane group concentration is 1.50 mmol/g or
more and 1.80 mmol/g or less.

4. The cleaning blade for an electrophotographic apparatus according to
claim 3 wherein the polyisocyanate is 4,4'-diphenyl methane diisocyanate.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to a cleaning blade used for an
electrophotographic apparatus using an electrostatic transfer process
such as an electrophotographic copier, a laser beam printer or a
facsimile.

[0003]2. Description of the Related Art

[0004]In an electrophotographic apparatus represented by a copier, a
printer, or a facsimile, toner is adhered to an electrostatic latent
image which is formed by uniformly charging the outer peripheral surface
of an image bearing member such as a photosensitive member and exposing
the surface through an image to be copied, thereby forming a toner image,
which is transferred to a transfer material such as paper to form an
image. Since toner remains on the outer peripheral surface of a
photosensitive member after transferring the toner image, a cleaning
blade is brought into contact with the outer peripheral surface of the
photosensitive member and frictionally slid to remove the remaining
toner, thereby preparing for the next image formation.

[0005]A cleaning blade is disposed by integrating a rubber blade member at
one end of a plate support fitting (holder) made of metal or the like and
fixing the holder on an apparatus. Since the blade member is excellent in
mechanical strength such as abrasion resistance and is low in creep
property such as permanent deformation due to contact stress, a
polyester-based urethane elastomer, especially a thermosetting
polyester-based urethane elastomer is used.

[0006]A urethane elastomer is produced using a polyisocyanate, a polyol, a
chain extender and a catalyst by a prepolymer method, a semi one-shot
method, a one-shot method or the like. For example, when a cleaning blade
is produced by a prepolymer method, the blade is produced by preparing a
prepolymer using a polyisocyanate and a polyol, and adding a chain
extender and a catalyst to this prepolymer, and then injecting the
resulting prepolymer into a die for molding to cure.

[0007]In order to completely remove remaining toner on a photosensitive
member by a cleaning blade, it is necessary that the contact of the
cleaning blade with the outer peripheral surface of the photosensitive
member is always maintained at a constant state. Therefore, the method in
which the positional relationship between the cleaning blade and the
photosensitive member is controlled or a support fitting is compressed by
a spring is generally performed.

[0008]However, when the hardness of a blade made of a urethane elastomer
is too high, the blade may damage a photosensitive member which is
brought into contact with the blade, and when the hardness is too low,
abrasion resistance becomes insufficient, and thereby chipping occurs on
the edge portion of the blade and toner may pass through from the chipped
portion of the blade to cause cleaning failure.

[0009]Due to high resolution of an electrophotographic apparatus in recent
years, toner to be used has a smaller diameter and a spherical shape, and
therefore toner easily passes through between a photosensitive member and
a cleaning blade and cleaning failure easily occurs as compared with
conventional electrophotographic apparatuses. Furthermore, along with the
widespread use of electrophotographic copier and a laser beam printer, an
electrophotographic apparatus has been used in broad environment as
compared with the conventional one, and cleaning failure easily occurs
due to reduction in rubber properties of a urethane elastomer used for a
blade member especially under low temperature environment (10° C.
or less). Particularly, cleaning failure easily occurs, especially when
an electrophotographic apparatus is first used in the morning after being
left to stand overnight under low temperature environment. It is reported
that the cleaning performance at low temperatures has correlation with a
peak tan δ temperature and can be improved by setting the peak tan
δ temperature at or below the temperature assumed at the use
temperature of an electrophotographic apparatus (Japanese Patent
Application Laid-Open No. H11-212418). In addition, it is reported that
the cleaning performance for spherical toner is improved by defining 300%
modulus and tear strength (Japanese Patent Application Laid-Open No.
2002-72799). However, it cannot be said that the cleaning blade of
Japanese Patent Application Laid-Open No. H11-212418 has sufficient
cleaning performance for spherical toner having a small diameter along
with high image quality of an electrophotographic apparatus, and it
cannot be said that the cleaning blade of Japanese Patent Application
Laid-Open No. 2002-72799 has sufficient cleaning performance under low
temperature environment.

SUMMARY OF THE INVENTION

[0010]An object of the present invention is to provide a cleaning blade
for an electrophotographic apparatus having good cleaning performance
both immediately after long-time shutdown under low temperature
environment and during continuous use under low temperature environment
even when spherical toner having a small diameter is used.

[0011]The present invention relates to a cleaning blade for an
electrophotographic apparatus having an elastic blade member which is
brought into contact with an image bearing member and frictionally slid
to remove remaining toner, wherein the elastic blade member satisfies (1)
to (4).

[0012](1) the stress-relaxation rate represented by the formula (a) at
10° C. is 25% or less;

Stress - relaxation rate = Variation of
stress when left to stand at
10 % stretching state for 1 hour
Stress at the moment of 10 %
stretching × 100 ( a ) ##EQU00002##

(2) The international rubber hardness (IRHD) is 65 or more and 80 or less;
(3) the stress upon 100% stretching in a tensile test is 3.0 MPa or more
and 5.0 MPa or less; and (4) the peak tan δ temperature in a
dynamic viscoelastic test is -20° C. or more and 0° C. or
less.

[0013]The cleaning blade for an electrophotographic apparatus of the
present invention has good cleaning performance both immediately after
long-time shutdown under low temperature environment and during
continuous use under low temperature environment even when spherical
toner having a small diameter is used.

[0014]Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference to the
attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a side view illustrating an example of the cleaning blade
for an electrophotographic apparatus of the present invention.

[0016]FIG. 2 is a schematic constitutional view illustrating an example of
an electrophotographic apparatus which can apply the cleaning blade for
an electrophotographic apparatus of the present invention.

DESCRIPTION OF THE EMBODIMENTS

[0017]The cleaning blade for an electrophotographic apparatus of the
present invention is a cleaning blade for an electrophotographic
apparatus having an elastic blade member which is brought into contact
with an image bearing member and frictionally slid to remove remaining
toner, wherein the elastic blade member satisfies (1) to (4):

(1) the stress-relaxation rate represented by the formula (a) at
10° C. is 25% or less;

Stress - relaxation rate = Variation of
stress when left to stand at
10 % stretching state for 1
hour Stress at the moment of
10 % stretching × 100 ( a ) ##EQU00003##

(2) the international rubber hardness (IRHD) is 65 or more and 80 or
less;(3) the stress upon 100% stretching in a tensile test is 3.0 MPa or
more and 5.0 MPa or less; and(4) the peak tan δ temperature in a
dynamic viscoelastic test is -20° C. or more and 0° C. or
less.

[0018]The elastic blade member has (1) a stress-relaxation rate determined
from the formula (a) at 10° C. of 25% or less. When the
stress-relaxation rate represented by the formula (a) at 10° C. is
25% or less in the elastic blade member, the linear pressure in the edge
portion of the elastic blade applied to the surface of a photosensitive
member can be prevented from being decreased when left to stand for a
long time under low temperature environment, and thereby cleaning failure
can be prevented from occurring.

[0019]As a stress-relaxation rate, a value determined by the following
method can be adopted. A strip specimen having a thickness of 0.5 mm is
cut from the blade member fabricated and this specimen is fixed on a
stress measuring apparatus (TMA/SS 6000: manufactured by Seiko
Instruments Inc.) so that the measuring length is 10 mm. The environment
in a cavity is set at 10° C. and the displacement of 1 mm is
applied to the specimen to maintain for 60 minutes. The stress at the
moment of applying the displacement and the stress after 60 minutes are
measured, and the stress-relaxation rate is calculated from the measured
values by the formula (a).

[0020]Further, the elastic blade member has (2) international rubber
hardness (IRHD) of 65 or more and 80 or less. In the elastic blade
member, when the hardness is 65° (IRHD) or more, toner can be
prevented from being passed through, and when the hardness is 80°
(IRHD) or less, a photosensitive member can be prevented from abrasion.

[0021]As an international rubber hardness (IRHD), a value measured using a
hardness meter manufactured by H. W. WALLACE & Co., Ltd. by a measuring
method according to JIS K6253 can be adopted.

[0022]Further, the elastic blade member has (3) a stress upon 100%
stretching in a tensile test (M100) of 3.0 MPa or more and 5.0 MPa or
less. In the elastic blade member, when M100 is 3.0 MPa or more, the
linear pressure of the edge portion applied to the surface of a
photosensitive member is sufficient, and thus deformation in the edge
portion can be prevented, and toner can be prevented from being passed
through and cleaning failure due to chipping of the edge portion can be
prevented from occurring. When M100 is 5.0 PMa or less, the linear
pressure of the edge portion applied to the surface of a photosensitive
member can be prevented from excessively increasing, and abrasion in the
edge portion or on the surface of a photosensitive member can be
prevented from occurring.

[0023]As a stress upon 100% stretching in a tensile test, a value measured
using a tensile tester (Unitron TS-3013: manufactured by Ueshima
Seisakusho Co., Ltd.) by a measuring method according to JIS K6251 can be
adopted.

[0024]Further, the elastic blade member has (4) a peak tan δ
temperature in a dynamic viscoelastic test of -20° C. or more and
0° C. or less. When the peak tan δ temperature in a dynamic
viscoelastic test is -20° C. or more, abrasion accompanied by
extreme movement of the edge portion can be prevented, and when the peak
temperature is 0° C. or less, the elastic blade member has
sufficient elasticity during continuous use under low temperature
environment, and thus can prevent occurrence of cleaning failure in low
temperature environment.

[0025]As a peak tan δ temperature, a value measured by the following
measuring method can be adopted. A strip specimen is cut from a blade
member and this specimen is fixed on Dynamic Mechanical Spectrometer (DMS
6100: manufactured by Seiko Instruments Inc.) so that the measuring
length is 20 mm. The specimen is subjected to distortion at an amplitude
of 5 μm and a frequency of 10 Hz, and tan δ of -30° C. to
60° C. is measured every about 0.5° C. at a rate of
temperature rise of 2° C./min. The temperature at which the value
of tan δ is maximum is taken as a peak tan δ temperature.

[0026]The elastic blade member satisfies (1) to (4), and thereby has good
cleaning performance under low temperature environment even when
spherical toner having a small diameter is used.

[0027]The elastic blade member can be one formed using a urethane
elastomer material.

[0028]Such a urethane elastomer material can be a liquid composition
containing a polyisocyanate, a polyol, a chain extender and a urethane
curing catalyst.

[0029]The polyisocyanate may be any one as long as it has two or more
isocyanate groups and examples thereof include the following:
4,4'-diphenyl methane diisocyanate (MDI), isophorone diisocyanate and
4,4'-dicyclohexyl diisocyanate; trimethylhexamethylene diisocyanate,
tolylene diisocyanate, carbodiimido-modified diisocyanate and
polymethylene phenyl polyisocyanate; and ortho-toluidine diisocyanate,
naphthalene diisocyanate, xylene diisocyanate, hexamethylene
diisocyanate, para-phenylene diisocyanate, lysine diisocyanate methyl
ester and dimethyl diisocyanate. These may be used alone or in
combination of two or more kinds. Among them, 4,4'-diphenyl methane
diisocyanate (MDI) can be particularly used.

[0030]The polyol used with the polyisocyanate may be any one as long as it
has two or more hydroxyl groups and examples thereof include the
following: polyethylene adipate polyester polyol, polybutylene adipate
polyester polyol, polyhexylene adipate polyester polyol and
polyethylene-propylene adipate polyester polyol; adipate-based polyester
polyols such as polyethylene-butylene adipate polyester polyol and
polyethylene-neopentylene adipate polyether polyol;
polycaprolactone-based polyester polyols obtained by ring-opening
polymerizing caprolactone and polyether polyols such as polyethylene
glycol, polypropylene glycol and polytetramethylene glycol; and
polycarbonate diols. These may be used alone or in combination of two or
more kinds.

[0031]The chain extender may be any one as long as it can extend a
urethane elastomer chain and a polyol can be used. Specifically, examples
thereof include the following: 1,4-butanediol, ethylene glycol,
diethylene glycol, propylene glycol, dipropylene glycol, hexane diol,
1,4-cyclohexane diol, 1,4-cyclohexane dimethanol and xylylene glycol; and
polyols having a molecular weight of 200 or less such as triethylene
glycol, trimethylol propane, glycerine, pentaerythritol, sorbitol and
1,2,6-hexane triol.

[0032]The urethane curing catalyst is divided broadly into an
isocyanuration catalyst and an urethanization catalyst, and one of them
may be used, but an isocyanuration catalyst and an urethanization
catalyst can be used in combination. As the urethane curing catalyst,
amine-based compounds such as a tertiary amine and organic metal
compounds can be used. Specifically, examples thereof include the
following. Examples of the isocyanuration catalyst include tertiary
amines such as N-ethylpiperidine, N,N'-dimethylpiperadine and
N-ethylmorpholine; hydroxides and weak organic acid salts of tetraalkyl
ammoniums such as tetramethyl ammonium, tetraethyl ammonium and
tetrabutyl ammonium; hydroxides and weak organic acid salts of
hydroxyalkyl ammoniums such as trimethylhydroxypropyl ammonium and
triethylhydroxypropyl ammonium; and alkali metal salts of carboxylic
acids such as acetic acid, propionic acid, butyric acid, caproic acid,
capric acid, valeric acid, octylic acid, myristic acid and naphthenic
acid. These may be used alone or in combination of two or more kinds.
Among them, alkali metal salts of carboxylic acids can prevent bloom
after molding and contamination of other parts, and thus is preferred.

[0033]As the urethanization catalyst, a polyurethane curing catalyst
generally used can be used and examples thereof include a tertiary amine
catalyst: amino alcohols such as dimethylethanolamine and
N,N,N'-trimethylaminopropylethanolamine; trialkylamines such as
triethylamine; tetraalkyldiamines such as
N,N,N',N'-tetramethyl-1,3-buthanediamine; and triethylenediamine,
piperadine-based catalyst and triadine-based catalyst. In addition, a
metal catalyst used for molding of polyurethane may be used and examples
thereof include dibutyl tin dilaurate. These may be used alone or in
combination of two or more kinds. Among them, amino alcohols are
preferred because they can prevent bloom after molding and contamination
of other parts together with reactivity, and N,N-dimethylaminohexanol is
further preferred.

[0034]The amount of an isocyanuration catalyst used can be 0.01% by mass
or less based on the total mass of a polyol and a polyisocyanate. When
the amount of an isocyanuration catalyst used is 0.01% by mass or less,
the amount of isocyanate becomes large, and thereby the stress-relaxation
rate can be prevented from excessively increasing.

[0035]The amount of a polyol can be 150 parts by mass or more and 300
parts by mass or less and the amount of a chain extender can be 10 parts
by mass or more and 20 parts by mass or less based on 100 parts by mass
of polyisocyanate in the urethane elastomer material. In addition, the
amount of a urethane curing catalyst used can be 0.02% by mass or more
and 0.05% by mass or less based on the total mass of a urethane elastomer
material.

[0036]Additives such as a catalyst, a pigment, a plasticizer, a
water-proofing agent, an antioxidant, an ultraviolet absorber and a light
stabilizer can be blended if necessary in the urethane elastomer
material.

[0037]In order to produce an elastic blade member using such a urethane
elastomer material, a prepolymer method, a one-shot method, a semipolymer
method, a pseudo-prepolymer method or the like can be used. As an example
thereof, the molding method for applying a prepolymer method will be
described below.

[0038]Firstly, a molding die for a cleaning blade is prepared, and a
holder serving as a support member is disposed. Next, a prepolymer which
is partially polymerized in advance by mixing a polyisocyanate and a
polyester polyol, a urethane curing catalyst and a chain extender are
charged into a casting machine, and stirred in a mixing chamber to obtain
a liquid mixture. This mixture is injected into the molding die and
reacted for curing, and then the cured product is removed from the die
and cut into a predetermined size, and thereby a cleaning blade in which
an elastic blade member made of polyurethane elastomer is molded on the
holder can be produced. An adhesive can be applied to a portion for
molding the elastic blade member of the holder.

[0039]In the above method, a method for molding an elastic blade member in
which a holder is disposed on a molding die has been described, but it is
also possible that an elastic blade member is molded without disposing a
holder on a molding die and then the resulting blade member is adhered to
a holder.

[0040]In an elastic blade member obtained from the urethane elastomer
material,

(5) the polyisocyanate concentration can be 0.95 mmol/g or more and 1.15
mmol/g or less;(6) the chain extender concentration can be 0.25 mmol/g or
more and 0.50 mmol/g or less; and(7) the urethane group concentration can
be 1.50 mmol/g or more and 1.80 mmol/g or less.

[0041]When an elastic blade member has (5) the polyisocyanate
concentration of 0.95 mmol/g or more, the amount of hard segments in a
urethane elastomer is sufficient, and thereby softening can be prevented
and the above conditions of (1) to (4) are satisfied. On the other hand,
when the polyisocyanate concentration is 1.15 mmol/g or less, the amount
of hard segments is excessively large, and thereby high hardness can be
prevented and the above conditions of (1) to (4) are satisfied.

[0042]When an elastic blade member has (6) the chain extender
concentration of 0.25 mmol/g or more, the amount of hard segments in a
urethane elastomer is sufficient, and thereby softening can be prevented
and the above conditions of (1) to (4) are satisfied. On the other hand,
when the chain extender concentration is 0.50 mmol/g or less, the amount
of hard segments is excessively large, and thereby high hardness can be
prevented and the above conditions of (1) to (4) are satisfied.

[0043]When an elastic blade member has (7) the urethane group
concentration of 1.50 mmol/g or more, agglomeration between molecular
chains is sufficient, and thereby softening can be prevented and the
above conditions of (1) to (4) are satisfied. On the other hand, when the
urethane group concentration is 1.80 mmol/g or less, agglomeration
between molecular chains is excessively large, and thereby high hardness
can be prevented and the above conditions of (1) to (4) are satisfied.

[0044]The polyisocyanate concentration and the chain extender
concentration in the blade member can be determined by the following
formulas (b) and (c) by calculating the number of moles from each of the
charged amounts (g) and the molecular weights. In addition, the urethane
group concentration can be determined by the following formula (d) from
the number of hydroxyl group of each of a polyol and a chain extender
determined by the following formulas (e) and (f). As the hydroxyl value
of polyol, the measured value obtained by a measuring method according to
JIS K1557-1 can be adopted.

[0045]An example of the cleaning blade for an electrophotographic
apparatus of the present invention is illustrated in FIG. 1. In the
cleaning blade for an electrophotographic apparatus illustrated in FIG.
1, a blade member 150 of the present invention is mounted on a holder
made of metal (rigid plate body) 130. Moreover, the position of a blade
member formed in the cleaning blade for an electrophotographic apparatus
and the shape can be appropriately selected so that the blade member can
be brought into contact with a photosensitive drum.

[0046]The cleaning blade for an electrophotographic apparatus of the
present invention is used, for example, for an electrophotographic
apparatus using an electrostatic transfer process such as a copier, a
laser beam printer, an LED printer, a facsimile and an
electrophotomechanical system. Moreover, a plurality of members such as
an image bearing member, a charging member and a developing member other
than a cleaning blade is integrally incorporated into these apparatuses
and can be applied as a process cartridge detachable to the main body of
the electrophotographic apparatus.

[0047]An example of an electrophotographic apparatus for applying the
cleaning blade for an electrophotographic apparatus of the present
invention includes an electrophotographic apparatus illustrated in FIG.
2. In the image forming apparatus illustrated in FIG. 2, an image bearing
member 51 such as a photosensitive member is rotationally driven at a
predetermined peripheral speed around a spindle in a clockwise direction
on the figure. The surface of this image bearing member 51 is uniformly
subjected to charging treatment by a charging member 52 such as a corona
discharger and a charging roller so as to have predetermined polarity and
potential. Next, the surface of the image bearing member 51 uniformly
subjected to charging treatment is subjected to exposure of objective
image information (laser beam scanning exposure, slit exposure of
original image and the like) by an exposure unit L, and thereby an
electrostatic latent image 53 corresponding to the objective image
information is formed. Thereafter, the electrostatic latent image 53 is
sequentially converted into a visible image as a toner image by a
developing member 54.

[0048]A toner image formed on the surface of the image bearing member 51
is then transferred to the surface side of a transfer material P by a
transfer member 55. Moreover, the transfer material P is conveyed to a
transfer portion between the image bearing member 51 and the transfer
member 55 at an appropriate timing by being synchronized with the
rotation of the image bearing member 51 from a paper feed unit not
illustrated in the figure. The transfer member 55 may be a roller type.
In addition, in a color LBP which outputs a color image using four color
toners, a color image of each color is sequentially superimposed and
transferred to an intermediate transfer body such as a roller or a belt,
and then transferred to the surface side of the transfer material P. The
transfer material P subjected to transfer of the toner image is separated
from the image bearing member 51 and is subjected to image fixation by a
fixing member 58 such as a heat fixing roller and is output as an image
formation product.

[0049]After transfer, the surface of the image bearing member 51 is made
to have a clean surface by removing adhered contamination such as
remaining toner by the cleaning blade for an electrophotographic
apparatus 56 of the present invention and is repeatedly prepared for
forming an image.

EXAMPLES

[0050]Next, the cleaning blade for an electrophotographic apparatus of the
present invention will be described in detail by way of examples, but the
technical scope of the present invention is not intended to be limited to
these examples.

Example 1

Preparation of Urethane Elastomer Material

[0051](A) 4,4'-Diphenyl methane diisocyanate (MDI) and (B) polybutylene
adipate polyester polyol (PBA, number average molecular weight 2000) were
mixed at a ratio shown in Table 1, and reacted at 80° C. for 120
minutes under nitrogen atmosphere to obtain a prepolymer. On the other
hand, (C) 1,4-butanediol (1,4-BD) and trimethylol propane (TMP), (D)
polyhexylene adipate polyester polyol (PHA, number average molecular
weight 1000) and (E) a catalyst were mixed at a ratio shown in Table 1 to
obtain a curing agent.

[0052]The molecular weights of the prepolymer and a polyol in the curing
agent were determined by the following method. For monodispersion
polystyrene for gel permeation chromatography (GPC), a calibration curve
of the peak count number and number average molecular weight of the
monodispersion polystyrene was made using GPC under the following
conditions. Column: G3000PWXL×2 (manufactured by Tosoh
Corporation); Elution solvent: 20 mM Phosphate buffer; Detector:
Differential refractometer; Flow rate: 0.5 mL/min; Amount of sample
solution used: 10 μL; and Column temperature: 45° C. The
average molecular weights were calculated from the determined calibration
curve.

[0054]A holder was previously prepared as a support member and an adhesive
was applied to the one end surface. The holder was disposed on a molding
die for a cleaning blade including an upper die and a lower die in a
state where the one end portion having an adhesive applied protruded into
a cavity, and the prepared urethane elastomer material was injected into
the inside of the cavity. This was reacted and cured at a heating
temperature of 130° C., and then the cured product was removed
from the die and cut into a predetermined size, and thereby a cleaning
blade for an electrophotographic apparatus in which an elastic blade
member is molded on a holder was fabricated.

[0055]The stress-relaxation rate, hardness, 100% modulus in a tensile
test, and the peak tan δ temperature for the obtained cleaning
blade were measured by the above method. The results are shown in Table
3.

[0058]The obtained cleaning blade for an electrophotographic apparatus was
incorporated into a laser beam printer (LBP-2510: manufactured by Canon
Inc.), and evaluations for cleaning properties after long-time shutdown
and cleaning properties in 500 continuous image formation (30%) at a low
temperature (10° C.) were performed. When an image failure due to
cleaning failure was not observed, the result was expressed as A, when
slight image failure was observed, the result was expressed as B, and
when significant image failure was observed, the result was expressed as
C. The results are shown in Table 3.

Examples 2 to 4 and Comparative Examples 1 to 3

[0059]A cleaning blade for an electrophotographic apparatus was fabricated
in the same manner as in Example 1 except that a prepolymer and a curing
agent were used at a ratio shown in Tables 1 and 2, and was evaluated.
The results are shown in Tables 3 and 4.

[0060]As shown in Tables 3 and 4, in Examples 1 to 4, cleaning failure did
not occur after long-time shutdown and after reproducing 500 sheets. On
the contrary, in Comparative Example 1, sufficient contact pressure could
not be obtained after long-time shutdown at low temperatures due to a
large stress-relaxation rate, and thereby cleaning failure occurred.
Moreover, M100 in a tensile test was larger than 5.0 MPa, and therefore
image failure occurred due to scraping the surface of a photosensitive
member drum. In Comparative Example 2, the peak tan δ temperature
was high, and therefore rubber properties at low temperatures were
insufficient and cleaning failure occurred. In addition, in Comparative
Example 3, the value of M100 in a tensile test was 3.0 MPa or less, and
therefore contact pressure necessary for cleaning could not be obtained
and cleaning failure occurred.

[0061]While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is not
limited to the disclosed exemplary embodiments. The scope of the
following claims is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures and functions.

[0062]This application claims the benefit of Japanese Patent Application
No. 2008-134220, filed May 22, 2008, which is hereby incorporated by
reference herein in its entirety.